U.S. patent number 4,278,540 [Application Number 06/148,494] was granted by the patent office on 1981-07-14 for back washing fluid filters.
Invention is credited to Mordeki Drori.
United States Patent |
4,278,540 |
Drori |
July 14, 1981 |
Back washing fluid filters
Abstract
A backwashable filtering device is described of the type
including a housing, a filter body, a backwash nozzle having a
nozzle inlet disposed adjacent to the upstream surface of the
filter body, and pressure sensor means for sensing the pressure
drop across the filter body and effective, upon sensing a
predetermined pressure drop, to initiate a backwashing operation by
connecting the backwash nozzle to the atmosphere and initiating
relative rotary movement between the filter body and the backwash
nozzle. The filtering device further includes a position sensor for
sensing the home angular position of the filter body with respect
to the backwash nozzle, and a control effective, only when said
home angular position is sensed, for terminating the backwash
operation.
Inventors: |
Drori; Mordeki (Kiron,
IL) |
Family
ID: |
11051071 |
Appl.
No.: |
06/148,494 |
Filed: |
May 9, 1980 |
Foreign Application Priority Data
Current U.S.
Class: |
210/107;
210/108 |
Current CPC
Class: |
B01D
29/668 (20130101) |
Current International
Class: |
B01D
29/00 (20060101); B01N 029/38 () |
Field of
Search: |
;210/107,108 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Adee; John
Attorney, Agent or Firm: Barish; Benjamin J.
Claims
What is claimed is:
1. A backwashable filtering device including a housing having an
inlet connectable to an upstream fluid pipe and an outlet
connectable to a downstream fluid pipe, a filter body having an
upstream surface facing the housing inlet, a backwash nozzle within
the housing and having a nozzle inlet disposed adjacent to the
upstream surface of the filter body, and pressure sensor means for
sensing the pressure drop across the filter body and effective,
upon sensing a predetermined pressure drop, to initiate a
backwashing operation by connecting the backwash nozzle to the
atmosphere and initiating relative rotary movement between the
filter body and the backwash nozzle; characterized in that the
filtering device further includes position sensor means for sensing
the home angular position of the filter body with respect to the
backwash nozzle, and control means effective, only when said home
angular position is sensed, for terminating the backwash
operation.
2. A device according to claim 1, wherein said angular position
sensor means sensing the angular position of the filter body with
respect to the backwash nozzle comprises a spring-biassed pin
carried by one engageable by the other.
3. A device according to claim 1, wherein the filter body is
rotatably mounted with respect to the backwash nozzle, the backwash
nozzle carrying said position sensor pin spring-biassed against an
annular surface of the filter body as the latter is rotated during
the backwash operation, said annular surface including an
interruption at the home position of the filter body
4. A device according to claim 1, wherein the filter body. said
control means comprises a pilot valve which, in the home position,
vents a chamber of the pressure sensor means to the atmosphere
permitting the pressure sensor means to terminate the backwash
operation.
5. A device according to claim 4, wherein said chamber is on one
side of a displaceable member coupled to a main valve which is
opened when said chamber is pressurized, there being a second
chamber on the other side of said displaceable member connected to
a high pressure source tending to move said main valve to its
closed position, said control means further including a fluid
passageway for connecting said first-mentioned chamber to said
high-pressure source when the pressure sensor means senses said
predetermined pressure drop to move said main valve to its open
position and thereby to initiate a backwashing operation.
6. A device according to claim 5, wherein said displaceable member
includes a plunger movable in a cylinder and including a diaphragm
dividing the cylinder into said first-mentioned and second
chambers.
7. A device according to claim 5, wherein said fluid passageway has
a larger cross-sectional area than said vent so as to start the
relative rotation between the filter body and the backwash nozzle
from the home position when a backwash operation is initiated.
8. A device according to claim 5, wherein said fluid passageway
comprises a one-way valve permitting the flow of fluid from the
pressurized source in one direction into said first-mentioned
chamber, but blocking the reverse flow of fluid therethrough from
said first-mentioned chamber.
9. A device according to claim 8, wherein said one-way valve
includes means for enabling the flow of the fluid in both
directions through said passageway to permit the backwash operation
to be terminated even when the position sensing means does not
sense the home angular position of the filter body with respect to
the backwash nozzle.
Description
BACKGROUND OF THE INVENTION
The present invention relates to backwashing fluid filters
including differential-pressure sensors which sense when the filter
body is overly clogged to initiate a backwashing operation for
backwashing the fluid feed through the filter body while relative
motion is effected between the filter body and a backwash nozzle
provided in the filter. The present invention is particularly
directed to the differential-pressure sensor included in such a
backwashing filter for sensing the condition of the filter body and
for controlling the initiation and termination of the backwashing
operation. The invention is especially, but not exclusively,
applicable to the differential-pressure sensor described in my
patent application No. 114,894, and is therefore described below
with respect to this application.
My above-cited patent application relates to a
differential-pressure valve, and also to a system including a
controlled device, such as a main valve, controlled by the
differential-pressure valve. One use for such a valve and system,
as mentioned in the above-cited patent application, is in
backwashable filtering devices which are automatically actuated to
backwash the filter whenever a predetermined quantity of dirt has
accumulated on the filter as sensed by the differential-pressure
valve sensing the difference in the pressure at points upstream and
downstream of the filter body. When a backwashing operation is
initiated, the backwash nozzle within the filtering device is
connected to the atmosphere to produce a backwashing flow of the
fluid through the filter body and out through the backwash nozzle.
In addition, relative rotary movement is effected between the
filter body and the backwash nozzle to cause the backwash nozzle to
scan and clean the complete outer surface of the filter body.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed to improvements related
particularly to the differential-pressure sensor when it is
included in a backwashable filtering device.
According to one aspect of the present invention, there is provided
a backwashable filtering device including a housing having an inlet
connectable to an upstream fluid pipe and an outlet connectable to
a downstream fluid pipe, a filter body having an upstream surface
facing the housing inlet, a backwash nozzle within the housing and
having a nozzle inlet disposed adjacent to the upstream surface of
the filter body, and pressure sensor means for sensing the pressure
drop across the filter body and effective, upon sensing a
predetermined pressure drop, to initiate a backwashing operation by
connecting the backwash nozzle to the atmosphere and initiating
relative rotary movement between the filter body and the backwash
nozzle; characterized in that the filtering device further includes
position sensor means for sensing the home angular position of the
filter body with respect to the backwash nozzle, and control means
effective, only when said home angular position is sensed, for
terminating the backwash operation.
Such an arrangement more positively assures that the complete
upstream surface of the filter body will be uniformly cleaned and
thereby prevents the possibility that dirt may build-up on a
portion of the filter body which dirt build-up could eventually
become wedged between the backwash nozzle and the filter body to
damage the latter or to interfere with the relative rotation
between the two.
In the preferred embodiment of the invention described below, the
angular position sensor means sensing the angular position of the
filter body with respect to the backwash nozzle comprises a
spring-biassed pin carried by one engageable by the other.
More particularly, in the described embodiment the filter body is
rotatably mounted with respect to the backwash nozzle, the backwash
nozzle carrying said position sensor pin spring-biassed against an
annular surface of the filter body as the latter is rotated during
the backwash operation, said annular surface including an
interruption at the home position of the filter body.
According to a further feature in the preferred embodiment
described below, the control means comprises a pilot valve which,
in the home position, vents a chamber of the pressure sensor means
to the atmosphere permitting the pressure sensor means to terminate
the backwash operation. The latter chamber is on one side of a
displaceable member coupled to a main valve which is opened when
the chamber is pressurized, there being a second chamber on the
other side of the displaceable member connected to a high pressure
source tending to move the main valve to its closed position. The
control means further includes a fluid passageway for connecting
the first-mentioned chamber to the high-pressure source when the
pressure sensor means senses the predetermined pressure drop to
move the main valve to its open position and thereby to initiate a
backwashing operation.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is herein described, by way of example only, with
reference to the accompanying drawings, wherein:
FIG. 1 is a longitudinal sectional view illustrating one form of
differential-pressure sensor constructed in accordance with the
invention and used in a backwashable filtering device, only a
fragment of which is illustrated.
FIGS. 1a and 1b illustrate this home position and non-home
position, respectively, of the litter body; and
FIG. 2 is a transverse sectional view along lines II--II of FIG. 1,
to more clearly illustrate the rotary drive for the backwashable
filtering device of FIG. 1.
DESCRIPTION OF A PREFERRED EMBODIMENT
As indicated earlier, the differential-pressure sensor illustrated
in FIG. 1 is of the type described in my prior patent application
No. 114,894, but it includes improvements or modifications
particularly to adapt it for controlling a backwashing operation in
a filtering device. To facilitate understanding the construction
and operation of the differential-pressure sensor illustrated in
FIG. 1, the same reference numerals, but increased by "100", are
used with respect to those elements which are generally common with
those in my patent application No. 114,894, the new elements being
identified by reference numerals beginning with "200".
Briefly, the differential-pressure sensor illustrated in FIG. 1 is
used to initiate a backwashable filtering device, whereupon piston
102 is moved within a cylinder 104 to uncover an opening 106 which
connects chamber 108 of the backwash nozzle to the atmosphere,
thereby backflushing the filter through the nozzle and through
opening 106.
More particularly, the differential-pressure sensor includes a
diaphragm 110 mounted between a pair of housing sections 112, 114
secured together by bolts 116. The sensor further includes a
circular rigid disc 118 secured within a central opening formed
through the diaphragm 110 by means of a plastic cap 120 threaded
onto exterior threads formed on stem 122 of the circular disc. The
circular disc 118 carries a rod-shaped valve member 124 movable in
or out of a valve opening 126 formed in an end wall 128 integral
with housing section 114.
A high-pressure source P.sub.H, taken from a point upstream of the
filter body to be described below, is inletted via port 130 into a
high-pressure chamber 132 at one side of diaphragm 110; and a
low-pressure source P.sub.L, taken from a point downstream of the
filter body, is inletted via port 134 into a low pressure chamber
136 at the opposite side of the sensor diaphragm 110. A coil spring
138 biasses the diaphragm to the closed position of its valve
member 124 with respect to valve passageway 126.
The main valve piston 102 is connected by a stem 154 to a plunger
156 movable within housing section 152. A spring 157 interposed
between piston 102 and an annular recess in housing section 152,
urges piston 102, and thereby plunger 156, in the direction
(rightwardly in FIG. 1) tending to decrease the volume of chamber
108.
End wall 128, through which is formed the valve passageway 126, is
common to the chambers 132 and 159, the latter chamber being
defined by the end wall 128 and the plunger 156 movable within
cylinder 152. Chamber 159 is connected to the high-pressure chamber
132 by a small bore 160 through end wall 128, this bore (e.g. 1 mm)
being considerably smaller in cross-sectional area than that of the
valve passageway 126 (e.g., 3 mm).
Valve passageway 126 is formed in a dished central part of end wall
128 and is lined with an O-ring 162 adapted to sealingly engage the
rod-shaped valve member 124 when the latter is in its closed
position. The movement of valve member 124 is guided by a guide
ring 164 carried on the opposite face of end wall 128 and formed
with an opening for guiding the movement of the valve member 124,
but permitting some clearance with respect thereto; that is, the
rod-shaped valve member 124 is not sealingly received within guide
ring 164.
An O-ring 170 is received within a circular recess formed on the
inner face (i.e. the face exposed to the high pressure chamber 132)
of the circular disc 118. O-ring 170 is of larger diameter than,
and circumscribes, both the guide ring 164 carried by the end wall
128, and the valve passageway 126 formed through the dished portion
of the end wall.
As described in the above-cited patent application, the
arrangement, insofar as described above, is such that when the
sensor diaphragm 110 is in the valve-closed position (i.e. with its
valve member 124 received within valve passageway 126 as shown in
FIG. 1), the O-ring 170 forms an annular sealing surface between
diaphragm 110 and end wall 128. This seals off that portion 172 of
the high pressure face of the diaphragm 110 enclosed by the O-ring
170, from the high-pressure within chamber 132, thereby increasing
the differential pressure (P.sub.H -P.sub.L) required to actuate
the sensor diaphragm 110 to move its valve member 124 out of the
valve passageway 126 to open the valve. On the other hand, when the
sensor diaphragm 110 is in the valve-closed position, this portion
172 of the high-pressure face of the diaphragm is exposed to the
high-pressure in chamber 132, thereby decreasing the differential
pressure required to move the diaphragm to its closed position.
Such an arrangement imparts a quick-action operation in opening and
closing the valve, and moreover, requires a higher differential
pressure to open the valve than to close it, both of which
characteristics are very advantageous when the sensor is used in
controlling a backwashing operation in a filtering device, as more
particularly described in my patent application No. 114,894.
One of the improvements in the sensor of the present application is
the provision of a diaphragm 200 between plunger 156 and housing
section 152, so as to divide the interior of the latter housing
section into the previously-mentioned chamber 159 at one side of
diaphragm 200, and another chamber 202 at the opposite side of
diaphragm 200. The latter chamber 202 is connected, via bore 203,
port 204, tube 206, and another port 208, to a chamber 210 within a
cylinder 212 fixed to housing section 104. Cylinder 212 includes a
valve opening normally closed by valve member 216 under the
influence of a spring 217 within cylinder 212, but may be moved
(leftwardly, FIG. 1) to open the valve 214 in order to vent chamber
210 to the atmosphere.
Moving the valve member 216 to the open position is effected by a
pin 218 biassed by spring 217 to move within an annular cam surface
220 rotating with the filter body. Cam surface 220 is in the form
of a recess or low surface for most of its length but includes a
projection or high surface 220' (FIG. 1a) in the home position of
the filter body which is engaged by pin 218, to open the valve 216.
As will be described more particularly below, when the rotatable
filter body is in this home position opening valve 216, pin 218
engages the high point 220' of cam surface 220 and therefore the
interior of chamber 202 is vented to the atmosphere via bore 203,
ports 204, 208, chamber 210, and valve 214. At all other positions
of the rotatable filter body, pin 218 engages a low-portion of
surface 220 and therefore valve 216 is closed.
In addition, the space 174 between the guide ring 164 and the valve
passageway 126, is connected via bore 222 through end wall 128, a
one-way valve 224, and another bore 226 through housing section
152, to chamber 202. Thus, as soon as the O-ring 170 moves away
from end wall 128 by the actuation of the sensor diaphragm 110, the
inlet pressure (P.sub.H) from inlet 130 is applied via space 174
and bores 222, 226 to chamber 202. This aids moving the piston 102
to its open position to uncover passageway 106, and thereby more
positively assures the opening of this passageway, and thereby the
initiation of a backwashing operation, even under low inlet
pressures when the inlet pressure might not be sufficient to
overcome the force of spring 157.
Bores 222 and 226 (e.g., both about 1.4 mm) are of larger
cross-sectional area than bore 203 (e.g. 1.0 mm) but are of
slightly smaller cross-sectional area than bore 176 (e.g. 1.5 mm).
The significance of the foregoing will be described below in
connection with the complete operation of the device. In addition,
one-way valve 224 permits the flow of fluid from space 174 into
chamber 202, but not vice versa, also for a reason to be described
more particularly below.
The backwash filtering device may be of any known construction,
e.g. as described in my application No. 92,583; therefore only that
portion cooperating with the differential-pressure sensor
controlling the backwashing operation is illustrated in FIG. 1.
Thus, the illustrated portion of the backwashable filtering device
comprises an inner rigid tube 302 defining the filter outlet 306 at
one end, an outer housing 316, a rotatable filter body 324
rotatably mounted between the inner metal tube 302 and the outer
housing 316, and a backwash nozzle 332 having an inlet opening
disposed adjacent to the outer cylindrical surface of the filter
body 324. The filter body 324 is rotated on a pair of end bearings
328 with respect to the fixed backwash nozzle 332 by means of a
hydraulic drive unit 342 actuated by the kinetic energy of the
fluid flowing through the backwash nozzle 332. Thus, as shown
particularly in FIG. 2, when piston 102 is actuated by the
previously-described pressure sensor including diaphragm 110 so as
to uncover opening 106, the fluid is backflushed through nozzle 332
and opening 106 to the hydraulic drive unit 342. The exiting dirty
fluid impinges blades 360 at one end of a rotor shaft 362 whose
opposite end is formed as a worm 364 meshing with a gear 366. The
latter gear is formed with teeth 368 along its circumference facing
the filter body 324, which body is formed with interfitting teeth
370 whereby the rotation of gear 366 also rotates the filter body
324.
The operation of the backwashable filtering device illustrated in
the drawings will now be described.
First, port 130 is connected to a high-pressure (P.sub.H) point
upstream of the filter body 324, and port 134 is connected to a
low-pressure (P.sub.L) point downstream of the filter body.
Assuming that the filter body 324 is relatively clean, there will
be very little difference between the two pressure points, and
therefore between the pressures in chambers 132 and 136, so that
spring 138 will maintain diaphragm 110 in its illustrated position
wherein its valve member 124 closes valve opening 126. At the same
time, chamber 159 will be pressurized via bore 160 leading from the
high-pressure chamber 132 to chamber 159, assuring that the plunger
156, and thereby the piston 102, will be in their illustrated
positions to the right of opening 106. The pressure within the
backwash nozzle 332 will therefore remain high so that the backwash
nozzle is not made operative. In this normal operating condition of
the filtering device, the rotary filter body 324 would be in its
home position wherein pin 218 of valve member 216 is engaged by the
projecting point 220' in cam surface 220 of the rotary filter body,
thereby venting chambers 212 and 202 to the atmosphere, assuring
that the pressure within chamber 159 will retain valve 102 in its
illustrated closed position with respect to opening 106.
Now, as dirt accumulates on the upstream surface (outer) of the
filter body 324, the pressure within chamber 136 begins to drop
with respect to that within chamber 132, until a point is reached
wherein the pressure difference is sufficient to cause diaphragm
110 to begin to move against the force of spring 138. As soon as
this occurs, O-ring 170 moves with the diaphragm away from the face
of the end wall 128, which exposes an enlarged surfaced area (i.e.
enlarged by the area within the O-ring) of the face of the sensor
diaphragm subjected to the high pressure of chamber 132. This
enlarges the force acting on the diaphragm to move it to the
opening position, and thereby produces a positive fast-acting
opening of the valve member 124 with respect to the valve
passageway 126.
As soon as this occurs, chamber 202 becomes pressurized via bores
222 and 226, thereby applying an increased force moving plunger
156, and thereby valve 102, leftwardly until the latter uncovers
passageway 106 to initiate a backwashing operation. Although at
this instant (i.e. before the filter body 324 has begun to rotate
during the backwashing operation) chamber 202 is still vented to
the atmosphere via bore 213 and valve member 216. Nevertheless
because bore 203 is of smaller cross-sectional area than bores 222
and 226 as described above, chamber 202 becomes pressurized
sufficient to initiate the backwashing operation, and as soon as it
is initiated, the rotary filter body 324 moves away from its home
position so as to close valve 214 and thereby to maintain the
pressure within chamber 202. At the same time, as soon as valve
member 124 opens the valve passageway 126, bore 176 vents chamber
159 to the atmosphere.
It will thus be seen that when a predetermined pressure drop has
been sensed across the filter body 324, thereby indicating an undue
accumulation of dirt on its upstream surface, valve member 102 will
uncover passageway 106 to vent the interior of the backwash nozzle
332 to the atmosphere. This initiates the backwash operation
wherein the backwashing fluid is discharged to the atmosphere via
the hydraulic drive unit 342. The kinetic energy in the discharged
fluid rotates blades 360 and thereby rotates the filter body 324.
As soon as the filter body moves from its home position, valve 216
is closed by the low cam surface 220 engaged by position sensor pin
218, thereby terminating the venting of chamber 202 to the
atmosphere, and permitting the chamber to remain pressurized.
The backwash operation will thus continue until the filter body is
sufficiently clean so as to lower the pressure differential applied
to the opposite faces of diaphragm 110 such that spring 138 returns
the diaphragm to the illustrated position wherein its valve member
124 moves into valve passageway 126. When this occurs, the pressure
within chamber 159 then builds up by the high-pressure applied
thereto from chamber 132 via bore 160. However, chamber 202 at the
opposite side of diaphragm 200 remains pressurized, first because
the one-way valve 224 does not permit the reverse flow of fluid
from the chamber 202, and secondly because valve member 216 closes
the valve passageway 214 at all non-home positions of the rotary
filter 324 thereby interrupting the venting of chamber 202 to the
atmosphere. Accordingly, the backwash operation and the rotation of
the filter body continue. However, as soon as the filter body 324
has rotated to its home position, the high surface 220' on its cam
face 220 moves the position sensor pin 218 leftwardly, moving valve
member 216 to open valve passageway 214, thereby venting the
interior of chamber 202 to the atmosphere.
Thus, when the filter body 324 has been cleaned during the
backwashing operation, diaphragm 110 returns to close passageway
126 thereby causing chamber 159 to be pressurized via bore 160
leading to the high-pressure chamber 130; and when the rotary
filter body 324 has returned to its home position, chamber 202 on
the other side of diaphragm 200 becomes vented to the atmosphere
via valve passageway 214 as described above. Accordingly, plunger
156 moved by the high pressure in chamber 159 rightwardly to cause
valve member 102 to close passageway 106, thereby terminating the
backwash operation.
If desired, the "homing feature" provided by the position sensor
pin 218 may be disabled by merely removing the ball in the one-way
valve 224. Thus, if that ball is removed, the bores 222 and 226
permit the flow of the fluid in both directions, i.e., not only in
the direction from the high-pressure chamber 132 to chamber 202 as
described previously when a backwash operation is initiated, but
also in the reverse direction from chamber 202 via bores 226 and
222, to space 174 and bore 176 to the atmosphere, when the filter
body has been sufficiently cleaned during the backwash operation so
as to restore the pressure sensor 110 to its home position as
illustrated in FIG. 1 of the drawings.
While the invention has been described with respect to one
preferred embodiment, it will be appreciated that many variations,
modifications and other applications of the invention may be
made.
* * * * *